Abrasion-resistant spun articles

ABSTRACT

The invention relates to spun articles, threads (yarns), fibers or filaments which have improved abrasion resistance properties and which can be used to produce felts for paper machines. The invention more specifically relates to synthetic resin-based threads (yarns), fibers or filaments having nanometric-sized loads.

[0001] The present invention relates to spun articles, yarns, fibers orfilaments which have improved abrasion resistance and which can be usedin particular to produce felts for paper machines. The invention relatesmore particularly to yarns, fibers or filaments based on synthetic resinand containing nanometric-sized fillers.

[0002] The properties which spun articles need to have are differentdepending on their use. Among these, mention may be made, for example,of mechanical strength, transparency, gloss, whiteness, dyeing ability,shrinkage, capacity for water retention, fire resistance, stability andheat resistance. One property which may be demanded, in particular forapplications in industrial fields or the fields of so-called technicalyarn, is abrasion resistance.

[0003] This is the case, for example, for the manufacture of nonwovenfelts from fibers. Increasing the abrasion resistance generally makes itpossible to increase the lifetime of the articles manufactured fromyarns, fibers or filaments. In the case of felts for paper machines,which are made from synthetic fibers, this property has become criticalfollowing the replacement of chemical bleaching agents with solidparticles, for example calcium carbonate.

[0004] This is also the case, for example, for the manufacture of rugsand carpets from fibers. In this case, the mechanical rubbing orabrasion stresses on the rug or carpet are such that the abrasionresistance property directly characterizes the lifetime of the rug orcarpet.

[0005] One known solution for improving the abrasion resistance of spunarticles is to increase the degree of curing of the synthetic materialfrom which they are made. This is the way in which fibers made fromthermoplastic resins of increasingly high viscosity are developed.Patent US-A-5 234 644 discloses, for example, a process for increasingthe viscosity of polymers. However, this solution has limits.Specifically, the spinning of fibers of very high viscosity requires theuse of very high spinning pressures and/or very high spinningtemperatures, which may result in degradation of the polymer.

[0006] Another solution for improving the abrasion resistance ofarticles made from fibers consists in using articles withthree-dimensional crimping.

[0007] The aim of the present invention is to propose another solutionfor obtaining spun articles with high abrasion resistance.

[0008] To this end, the invention proposes yarns, fibers and filamentsbased on synthetic resin, characterized in that they comprise between0.05% and 20% by weight of nanometric-sized particles dispersed in theresin and in that they have an abrasion resistance which is improved byat least 5%,compared with yarns, fibers and filaments made from anidentical resin, of the same viscosity but not containingnanometric-sized particles. The abrasion resistance is defined by thenumber of to and fro motions of a three-roll roller assembly, over a setof 15 fixed yarns, that is required to break 13 of the yarns.

[0009] This solution furthermore has the advantage of being able to becombined with an improvement in the abrasion resistance by increasingthe viscosity of the resin.

[0010] The expression “nanometric-sized particle” means any object forwhich at least one characteristic size parameter (diameter, length,thickness) is less than or equal to 100 nanometers, preferably less thanor equal to 50 nm. The particles may be, for example, substantiallyspherical, with a nanometric-sized diameter. The particles may be in theshape of platelets or needles, i.e. shapes for which it is possible todefine at least one large size parameter and at least one small sizeparameter. In this case, the small size parameter is advantageously lessthan 50 nm and preferably 10 nm. For example, the particles may beplatelets less than 10 nm thick with a form factor, .i.e. a ratio oflarge size to small size, of greater than 10.

[0011] The weight proportion of the particles relative to the totalweight of the material is between 0.05% and 20%. It is advantageouslyless than or equal to 5%.

[0012] The synthetic resin constituting the matrix in which theparticles are dispersed may be chosen from any spinnable polymer. Itconsists, for example, of polyamide or polyester, a blend of polymerscomprising polyamide or polyester, or copolymers based on polyamide orpolyester. As examples of polyamides which are suitable for carrying outthe invention, mention may be made in particular of Nylon-6 andNylon-6,6, and blends and copolymers thereof.

[0013] The yarns, fibers and filaments according to the invention maycontain any additive usually used with such polymers, for example heatstabilizers, UV stabilizers, catalysts, pigments, dyes and antibacterialagents.

[0014] According to a first embodiment of the invention, the particlesdispersed in the synthetic resin matrix are of substantially sphericalshape with a mean diameter of less than or equal to 100 nanometers.According to one preferred embodiment, the mean diameter of theseparticles is less than or equal to 50 nanometers.

[0015] The particles may be chosen from particles based on inorganicmaterials. They may be metallic or mineral, obtained from a naturalsource or may be synthesized. Examples of suitable materials which maybe mentioned include silver, copper, gold and the oxides and sulfides ofmetals, for example of silicon, zirconium, titanium, cadmium or zinc.Silica-based particles may be used in particular.

[0016] The particles may have been subjected to treatments to make themcompatible with the matrix. These treatments are, for example, surfacetreatments or a surface deposition of a compound other than thatconstituting the core of the particles. Treatments and depositions maysimilarly be carried out in order to promote the dispersion of theparticles, either in the polymerization medium of the matrix or in themolten polymer.

[0017] The surface of the particles may comprise a protective layerintended to prevent any degradation of the polymer in contact with theseparticles. Metal oxides, for example silica, in a continuous ordiscontinuous layer, may thus be deposited at the surface of theparticles.

[0018] Any method for obtaining a dispersion of particles in a resin maybe used to carry out the invention. A first process consists inmelt-blending the particles in resin and in optionally subjecting themixture to high shear, for example in a twin-screw extrusion device, inorder to achieve good dispersion. Another process consists in mixing theparticles with the monomers in the curing medium, and then in curing theresin. Another process consists in melt-blending a concentrated mixtureof a resin and particles, prepared, for example, according to one of theprocesses described above.

[0019] There is no limitation on the form in which the particles areintroduced and mixed with the monomers or the melt. The particles may beintroduced in the form of powder or in the form of an optionallystablilized aqueous solution. For example, a silica sol may beintroduced into the curing medium of the resin.

[0020] According to a second embodiment of the resin, the particlesdispersed in the synthetic resin matrix are in the form of plateletsless than 10 nanometers thick. Preferably, the thickness is less than 5nanometers. The particles are preferably dispersed in the matrix inindividual form. However, aggregates may exist and are preferably lessthan 100 nm thick and even more preferably less than 50 nm thick.

[0021] The platelets are advantageously obtained from exfoliablesilicate leaflets. The exfoliation may be promoted by a prior treatmentwith a swelling agent, for example by exchange of the cations initiallycontained in the silicates with organic cations such as oniums. Theorganic cations may be chosen from phosphoniums and-ammoniums, forexample primary to quaternary ammoniums. Mention may be made, forexample, of protonated amino acids such as 12-aminododecanoic acid,protonated primary to tertiary ammoniums, and quaternary ammoniums. Thechains attached to the nitrogen or phosphorus atom of the onium may bealiphatic, aromatic, aryaliphatic, linear or branched and may containoxygenated units, for example hydroxyl or ethoxy units. As examples oforganic ammonium treatments, mention may be made of dodecylammonium,octadecylammonium, bis(2-hydroxyethyl)octadecylmethyl-ammonium,dimethyldioctadecylammonium, octadecylbenzyl-dimethylammonium andtetramethylammonium. As examples of organic phosphonium treatments,mention may be made of alkylphosphoniums such as tetrabutylphosphonium,trioctyloctadecylphosphonium and octadecyltriphenyl-phosphonium. Theselists do not have any limiting nature.

[0022] The silicate leaflets which are suitable for carrying-out theinvention may be chosen from montmorillonites, smectites, illites,sepiolites, palygorkites, muscovites, allervardites, amesites,hectorites, talcs, fluorohectorites, saponites, beidellites,nontronites, stevensites, bentonites, micas, fluoromicas, vermiculites,fluorovermiculites and halloysites. These compounds may be of natural,synthetic or modified natural origin.

[0023] According to one preferred embodiment of the invention, theyarns, fibers and filaments are composed of polyamide resin and ofplatelet particles dispersed in the resin, obtained by exfoliation of aphyllosilicate, for example a montmorillonite which has undergone aprior swelling treatment by ion exchange. Examples of swellingtreatments which may be used are disclosed, for example, in patentEP-A-0 398 551. All the known treatments for promoting the exfoliationof phyllosilicates in a polymer matrix may be used. It is possible, forexample, to use a clay treated with an organic compound sold by thecompany Laporte under the brand name Cloisite®.

[0024] Any method for obtaining a dispersion of particles in a resin maybe used to carry out the invention. A first process consists in mixingthe compound to be dispersed, optionally treated, for example, with aswelling agent, in the melt and in optionally subjecting the mixture tohigh shear, for example in a twin-screw extrusion device, in order toachieve good dispersion. Another process consists in mixing the compoundto be dispersed, optionally treated, for example, with a swelling agent,with the monomers in the curing medium, and then in curing the resin.Another process consists in melt-blending a concentrated mixture of aresin and dispersed particles, prepared, for example, according to oneof the processes described above.

[0025] There is no limitation on the form in which the particles areintroduced and mixed with the monomers or the melt. The particles may beintroduced in the form of a powder of exfoliable compound or in the formof a dispersion in water or in an organic dispersant of an exfoliablecompound.

[0026] The spun articles, yarns, fibers or filaments are made accordingto the usual spinning techniques from a material comprising thesynthetic resin and the particles. The spinning may be carried outimmediately after curing the resin, this resin being in molten form. Itmay be carried out using a granular composite comprising the particlesand the synthetic resin. The particles may be incorporated into themolten polymer before the spinning operation in the form of aconcentrated mixture in a polymer. Any method for incorporatingparticles into a polymer to be spun may be used.

[0027] The spun articles according to the invention may be subjected toany treatment which may be carried out in steps subsequent to thespinning step. They may in particular be drawn, textured, crimped,heated, twisted, dyed, sized, chopped, etc. These additional operationsmay be carried out continuously and may be incorporated after thespinning device or may be carried out in batchwise mode. The list ofoperations subsequent to the spinning operation has no limiting nature.

[0028] The spun articles according to the invention may be used inwoven, knitted or nonwoven form. The fibers according to the inventionare suitable in particular for the manufacture of felts for papermachines. They may also be used for the manufacture of yarns forcarpets.

[0029] Other details or advantages of the invention will emerge moreclearly in the light of the example below, which is given purely as aguide.

[0030] The properties and characteristics of the yarns according to theinvention are determined according to the following methods:

[0031] Mechanical characterization (elongation at break, tensilestrength): carried out on an Erichsen tensile machine placed in anair-conditioned location at 50% RH and 23° C. after conditioning theyarns for 72 hours under these conditions. The initial length of theyarns is 50 mm and the traveling speed is 50 mm/min.

[0032] Abrasion resistance: a simultaneous friction is applied to 15immobile yarns whose tension is kept constant at 15 yarns by 3 brassrolls forming a roller assembly. The point of application of the rollingzone is moved along the yarns over an amplitude of 90 mm at a frequencyof 220 cycles per minute. The abrasion resistance is defined by thenumber of cycles (to and fro) required to break 13 of the 15 yarns. Themeasurements given are the averages of the values obtained on threetests with similar yarns.

EXAMPLES 1 and 2

[0033] A sol of silica nanospheres of the brand name Klebosol® with amean diameter equal to 50 nm, sold by the company Hoechst, is introducedinto caprolactam. The sol is introduced as an aqueous phase at a weightconcentration of 30%.

[0034] The curing of the caprolactam is carried out according to a usualprocess. After curing, a polymer is obtained with an absolute molar massof 34 980 g/mol, determined by GC, and a viscosity index of 140 ml/g.The polymer is washed and then dried for 16 hours at 110° C. under aprimary vacuum.

[0035] The polymer is then spun at low speed in the form of a roundmonofilament through a die about 1 mm in diameter. The yarn obtained hasa diameter of about 250 μm. The yarn is then drawn by pinching betweentwo rollers. The draw ratio is equal to the ratio of the rotation speedsof the rollers. Different draw ratios are applied.

[0036] The characteristics of the yarns obtained are as follows:Elongation Tensile 5% Secant Abrasion at break strength modulusresistance Draw ratio (%) (MPa) (MPa) (cycles) Example 1 4.37 28.8 7522.44 1 875 Example 2 5.04 21.9 868 3.04 1 375

EXAMPLES 3 and 4

[0037] 5% by weight of a clay treated with an organic compound sold bythe company Laporte under the name Cloisite 25A, a sodiummontmorillonite which has undergone an ion exchange withdimethyl-2-ethylhexyl-(hydrogenated tallow)ammonium methyl sulfate, of95 to 100 milliequivalents per 100 g of montmorillonite, is introducedinto Nylon-6. Nylon-6 is a commercial compound with a viscosity index of140 ml/g, sold under the name Technyl®. The incorporation is carried outin a Leistritz twin-screw extruder with a diameter of 34 mm.

[0038] The compound obtained is spun and drawn under the same conditionsas those described in Examples 1 and 2.

[0039] The characteristics of the yarns obtained are as follows:Elongation Tensile 5% Secant Abrasion at break strength modulusresistance Draw ratio (%) (MPa) (MPa) (cycles) Example 3 4.28 27.4 4914.68 5 200 Example 4 5.02 19.3 777 6.51 3 800

EXAMPLES 5 and 6

[0040] 3% by weight of a clay treated with an organic compound sold bythe company Laporte under the name Cloisite 25A, a sodiummontmorillonite which has undergone an ion exchange withdimethyl-2-ethylhexyl-(hydrogenated tallow)ammonium methyl sulfate, of95 to 100 milliequivalents per 100 g of montmorillonite, is introducedinto Nylon-6. Nylon-6 is a commercial compound with a viscosity index of140 ml/g, sold under the name Technyl®. The incorporation is carried outin a Leistritz twin-screw extruder with a diameter of 34 mm.

[0041] The compound obtained is spun and drawn under the same conditionsas those described in Examples 1 and 2.

[0042] The characteristics of the yarns obtained are as follows:Elongation Tensile 5% Secant Abrasion at break strength modulusresistance Draw ratio (%) (MPa) (MPa) (cycles) Example 5 4.10 30.0 5193.52 6 300 Example 6 4.65 19.6 625 4.21 5 500

EXAMPLES 7 and 8

[0043] 1% by weight of a clay treated with an organic compound sold bythe company Laporte under the name Cloisite 25A, a sodiummontmorillonite which has undergone an ion exchange withdimethyl-2-ethylhexyl-(hydrogenated tallow)ammonium methyl sulfate, of95 to 100 milliequivalents per 100 g of montmorillonite, is introducedinto Nylon-6. Nylon-6 is a commercial compound with a viscosity index of140 ml/g, sold under the name Technyl®. The incorporation is carried outin a Leistritz twin-screw extruder with a diameter of 34 mm.

[0044] The compound obtained is spun and drawn under the same conditionsas those described in Examples 1 and 2.

[0045] The characteristics of the yarns obtained are as follows:Elongation Tensile 5% Secant Abrasion at break strength modulusresistance Draw ratio (%) (MPa) (MPa) (cycles) Example 7 4.15 31.0 5633.84 6 400 Example 8 4.78 24.3 685 4.57 4 400

EXAMPLES 9 and 10

[0046] 5% by weight of a clay treated with an organic compound sold bythe company Laporte, a sodium montmorillonite which has undergone an ionexchange with dimethyldioctadecylammonium chloride, of 120milliequivalents per lo g of montmorillonite, is introduced intoNylon-6. Nylon-6 is a commercial compound with a viscosity index of 140ml/g, sold under the name Technyl®. The incorporation is carried out ina Leistritz twin-screw extruder with a diameter of 34 mm.

[0047] The compound obtained is spun and drawn under the same conditionsas those described in Examples 1 and 2.

[0048] The characteristics of the yarns obtained are as follows:Elongation Tensile 5% Secant Abrasion at break strength modulusresistance Draw ratio (%) (MPa) (MPa) (cycles) Example 9  4.62 23.8 5282.66 2 300 Example 10 5.33 17.0 650 4.28 1 575

EXAMPLES 11 and 12

[0049] 5% by weight of a clay treated with an organic compound sold bythe company Laporte, a sodium montmorillonite which has undergone an ionexchange with methyl-N,N-bis(hydroxyethyl)(ester of hydrogenated2-hydroxyethyl tallow)ammonium methyl sulfate, of 95 to 120milliequivalents per 100 g of montmorillonite, is introduced intoNylon-6,6. Nylon-6,6 is a commercial compound with a viscosity index of140 ml/g, sold by the company Nyltech. The incorporation is carried outin a Leistritz twin-screw extruder with a diameter of 34 mm.

[0050] The compound obtained is spun and drawn under the same conditionsas those described, in Examples 1 and 2.

[0051] The characteristics of the yarns obtained are as follows:Elongation Tensile 5% Secant Abrasion at break strength modulusresistance Draw ratio (%) (MPa) (MPa) (cycles) Example 11 3.94 25.0 3723.7 5 200 Example 12 4.72 17.1 501 4.7 4 200

Comparative Examples 1 and 2

[0052] A Nylon-6 with a viscosity of 140 ml/g is spun and drawn underthe same conditions as those described in Examples 3 to 10.

[0053] The characteristics of the yarns obtained are as follows:Elongation Tensile 5% Secant Abrasion at break strength modulusresistance Draw ratio (%) (MPa) (MPa) (cycles) Comparative 4.34 33.7 6603.72 1 700 Example 11 Comparative 5.16 20.0 975 5.74 1 000 Example 21

Comparative Examples 3 and 4

[0054] A Nylon-6,6 with a viscosity index of 140 ml/g is spun and drawnunder the same conditions as those described in Examples 11 and 12.

[0055] The characteristics of the yarns obtained are as follows:Elongation Tensile 5% Secant Abrasion at break strength modulusresistance Draw ratio (%) (MPa) (MPa) (cycles) Comparative 4.09 37.5 4803.3 5 050 Example 3 Comparative 4.85 22.2 672 4.2 3 000 Example 4

1. Yarns, fibers and filaments based on synthetic resin, characterizedin that they comprise between 0.05% and 20% by weight ofnanometric-sized particles dispersed in the resin and in that they havean abrasion resistance which is improved by at least 5% compared withyarns, fibers and filaments made from an identical resin, of the sameviscosity but not containing nanometric-sized particles, the abrasionresistance being defined by the number of to and fro motions of athree-roll roller assembly, over a set of 15 fixed yarns, that isrequired to break 13 of the yarns.
 2. The yarns, fibers and filaments asclaimed in claim 1, characterized in that the abrasion resistance isimproved by at least 10%.
 3. The yarns, fibers and filaments as claimedin claim 1, characterized in that the weight concentration of particlesis less than or equal to 5%.
 4. The yarns, fibers and filaments asclaimed in one of the preceding claims, characterized in that thesynthetic resin is chosen from polyamides, blends containing polyamides,and copolymers based on polyamides.
 5. The yarns, fibers and filamentsas claimed in claim 4, characterized in that the synthetic resin isbased on Nylon-6, Nylon-6,6 or blends or: copolymers thereof.
 6. Theyarns, fibers and filaments as claimed in one of the preceding claims,characterized in that the particles are of substantially spherical shapeand have a mean diameter of less than or equal to 100 nanometers.
 7. Theyarns, fibers and filaments as claimed in claim 6, characterized in thatthe mean diameter of the particles is less than or equal to 50nanometers.
 8. The yarns, fibers and filaments as claimed in either ofclaims 6 and 7, characterized in that the particles are inorganicparticles based on oxides or sulfides of titanium, silicon, zirconium,cadmium or zinc or are based on mixtures of these compounds.
 9. Theyarns, fibers and filaments as claimed in one of claims 6 to 8,characterized in that the particles are based on silica.
 10. The yarns,fibers and filaments as claimed in claim 9, characterized in that thesilica-based particles are introduced in the form of a sol into thecuring medium of the resin.
 11. The yarns, fibers and filaments asclaimed in one of claims 1 to 5, characterized in that the particles arein platelet form, the mean thickness of the platelets being less than 10nanometers.
 12. The yarns, fibers and filaments as claimed in claim 11,characterized in that the platelets are exfoliable silicates.
 13. Theyarns, fibers and filaments as claimed in claim 11, characterized inthat the platelets are exfoliable silicates treated with a swellingagent.
 14. The yarns, fibers and filaments as claimed in one of claims11 to 13, characterized in that the platelets are obtained frommaterials chosen from montmorillonites, smectites, illites, sepiolites,palygorkites, muscovites, allervardites, amesites, hectorites, talcs,fluorohectorites, saponites, beidellites, nontronites, stevensites,bentonites, micas, fluoromicas, vermiculites, fluorovermiculites andhalloysites.
 15. The yarns, fibers and filaments as claimed in one ofclaims 11 to 14, characterized in that the platelets are of synthetic ornatural origin.
 16. The yarns, fibers and filaments as claimed in one ofclaims 11 to 15, characterized in that the particles are incorporatedinto the resin by introduction into the curing medium of the resin. 17.The yarns, fibers and filaments as claimed in one of claims 11 to 15,characterized in that the particles are incorporated into the resin byintroduction into the melt.
 18. A felt for a paper machine, made fromyarns, fibers and filaments as claimed in one of claims 1 to
 17. 19.Rugs and carpets made from yarns, fibers or filaments as claimed in oneof claims 1 to 17.